Adsorbers for in-situ collection and at-sea gamma analysis of dissolved Thorium-234 in seawater

Reply to comment by Chin‐Chang Hung et al. on “How accurate are 234Th measurements in seawater based on the MnO2‐impregnated cartridge technique?”

“…For example, at a comparable flow rate, Moran et al [1997] obtained much higher efficiency (90 ± 7%) using 5 μ m cartridges than Livingston and Cochran [1987] using 1 μ m cartridges (83 ± 8%). The most important criteria to assess the quality of MnO 2 cartridges is to examine the theoretical extraction efficiency using the equation E = 1 − B/A [e.g., Guo et al , 2002; Hartman and Buesseler , 1994]. In our study, much lower 234 Th activities were detected in cartridge B than in cartridge A, and the theoretical extraction efficiency of our cartridges was as high as previous studies [ Cai et al , 2006a] (also see Table 1).…”

Comment on “How accurate are 234Th measurements in seawater based on the MnO2‐impregnated cartridge technique?” by Pinghe Cai et al.

“…Several different types, lengths and pore sizes of cartridges have been used (Table 1). Cartridges are generally wound fiber polypropylene with pore sizes of 0.5 μ m [e.g., Buesseler et al , 1992; Cochran et al , 1993, 1995; Bacon et al , 1996; Baskaran et al , 1993, 1996; Santschi et al , 1999; Guo et al , 2002; Hung et al , 2004], 1 μ m [ Livingston and Cochran , 1987; Cochran et al , 1987; Colley and Thomson , 1994] or 5 μ m [ Hartman and Buesseler , 1994; Moran et al , 1997]. The cartridges are usually preceded by prefilters that are either untreated cartridges or a series of filters of different pore sizes (e.g., Nitex or Teflon, Whatman GF/F or QM‐A) that separate particulate Th.…”

A review of present techniques and methodological advances in analyzing 234Th in aquatic systems

“…As an alternative to the ashing process, the cartridges may be melted or crushed (Hartman and Buesseler 1994) into a standardized geometry (Buesseler et al 1992). Entire cartridges may also be leached in an acid (>3N HCl) re-circulating system (Rutgers van der Loeff and Berger 1993).…”